It is much less costly just to buy a bottle of dechlorination solution than it is to purchase spring water, Mantisman. One drop of solution dechlorinates one gallon, and you can get a bottle of the stuff for four dollars.

I don't have experience myself with well water, but I don't imagine any issue so long as there's nothing wrong with the water itself (very acidic, looks foggy, etc). As for buying them from pet stores, almost all places get their toads from the wild anyway. You really just need to look at their condition.

For the light, it should be fine. So long as the tank is warm enough, you're good. FBTs aren't particularly needy as far as UVB lighting goes, though you'll need UVB to grow plants.

As for the heating pad, just do not put it on any glass that is in contact with water. You'll crack the glass in no time at all. What you could get is a water heater which attaches via suction-cup to the glass. Just be sure it's not in a spot where your FBTs will stop for a rest and place their feet on it. I tend to put them in the filters, as the running water makes it more efficient and I can easily cover it up. Of course, I design and put together filters myself, so one which you purchase would probably not have a place for a water heater.